An organic EL element has an anode electrode, a cathode electrode, and organic thin film layers (an electron injection layer, a light emission layer, a hole injection layer, and the like) formed between the electrodes. The organic EL element emits light by energy generated by recombination of holes supplied from the hole injection layer and electrons supplied from the electron injection layer, in the light emission layer. The light emission is realized by applying voltage equal to or higher than a predetermined voltage threshold to the organic thin film layers, and the brightness of the light is controlled by the application voltage. As disclosed in Unexamined Japanese Patent Application KOKAI Publication No. 2001-195012, such an organic EL element is used for display devices of various kinds of electronic devices, and is driven by a drive circuit including a TFT (Thin Film Transistor), a capacitor, and the like. The organic EL element is formed together with the drive circuit on a substrate.
The layout of the drive circuit on a substrate is very important. In particular, the larger the area of a capacitor for storing charges of an amount according to the potential difference between a gate and a source of a TFT and holding the potential difference is, the better.